1. Field of the Invention
The present invention relates to a concrete molding form member for assembling a concrete formwork which is employed for placing concrete or molding a concrete secondary product in construction and civil engineering works, and a form member space holder and a form member connector which are employed for assembling the form member.
2. Description of the Background Art
In general, a wood form member comprising a plywood board and bridges which are nailed thereto and a metal form member comprising an iron plate or an aluminum plate and metal ribs which are fixed thereto are known as such concrete molding form members. As shown in FIG. 54A, a typical example of the conventional wood form member 70 comprises a flat plate 71 of plywood which is fixed to a plurality of reinforcing bridges 73 with nails 72, for example. In order to assemble a concrete formwork, endmost reinforcing bridges 72 of adjacent form members 70 are fastened to each other with nails 73, for coupling/fixing the form members 70 with/to each other. FIG. 54B shows an exemplary concrete formwork which is assembled in the aforementioned manner to have a cross concrete molding part 74. The flat plates 71 can be formed by plastic plates, for example, in place of the plywood boards.
Description is now made on an example of a conventional form member space holder for fixing a pair of the aforementioned form members 70 with a prescribed space through concrete placing surfaces for assembling a concrete formwork, with reference to FIGS. 55 and 56A to 56C. Referring to FIG. 55, the conventional form member space holder is mainly formed by a separator 121, attachments 122 and clamp members 123. As shown in FIG. 56A, the separator 121 comprises a bar and a pair of male screws 121a which are provided on both ends thereof. Each male screw 121a is fitted with a female screw 122c which is provided on a first end of each attachment 122 as shown in FIG. 56B. A male screw 122d which is provided on a second end of the attachment 122 substantially coaxially with the female screw 122c passes through a separator mounting hole 76 which is provided in each form member 70, so that an end of a substantially truncated-conical resin presser part 122a which is engaged with the outer periphery of an attachment body part 122b is in contact with the concrete placing surface of the form member 70. A female screw 123a which is provided on a first end of each clamp member 123 is fitted with the male screw 122d of the attachment 122, thereby clamping/fixing the attachment 122 to each form member 70.
A male screw 123b is provided on a second end of each clamp member 123 as shown in FIG. 56C, so that a support member 124 and a nut 125 which are mounted on this male screw 123b fix thin cylindrical form member support members 126 of a metal for bridging a plurality of transversely arranged form members 70, as shown in FIG. 55.
FIG. 57A shows a typical example of a conventional metal form member 80 comprising a metal flat plate 81, and side plates 82 and reinforcing plates 83 which are bonded/fixed to the same. FIG. 57B shows a concrete formwork having a cross concrete molding part 84, which is assembled by a plurality of such metal form members 80. In this formwork, metal reinforcements 85 are employed in intersections of the cross concrete molding part 84, in addition to the form members 80.
Japanese Utility Model Laying-Open No. 62-54149 (1987) discloses a conventional synthetic resin form member which is also well known in the art. In the synthetic resin form member described in this gazette, reinforcing projections which are made of plastic are integrally provided on four points of a back surface portion of a plate member having a square front surface. The projections are provided with holes for receiving links, while the plate member is also provided with holes for receiving separators in prescribed portions thereof.
Japanese Patent Laying-Open No. 2-8459 (1990) discloses a concrete placing form member consisting of a press-molded sheet containing 50 to 10 percent by weight of glass fiber mat in 50 to 90 percent by weight of thermosetting resin. On the other hand, Japanese Patent Laying-Open No. 5-59811 (1993) discloses a concrete placing form member comprising a face plate and reinforcing ribs which are provided at least along the longitudinal direction of the face plate. In this form member, the face plate is formed by a fiber reinforced plastic member, while a fiber reinforced plastic material forming the ribs (longitudinal ribs) along the longitudinal direction has a bending elastic modulus of at least 10 GPa and longitudinal flexural rigidity of the form member is set to be at least 2.5.times.10.sup.7 kgf.multidot.mm.sup.2 per unit width (1 cm) of the form member.
Among the aforementioned conventional examples, the wood form member can be recycled merely 3 to 4 times since the plywood board is separated from its end portion upon employment of several times due to absorption of alkaline moisture, requires skillfulness for assembling/execution, is unsuitable for global environmental protection due to consumption of lauan raw material and industrial waste resulting from the spent form member, and cannot be applied to high-quality concrete having a low slump value and high strength since employment of a vibrator is limited due to low strength, although the same is lightweight and has a degree of freedom in execution.
Due to high water absorptivity of the plywood board, further, the concrete as placed loses an ideal water-cement ratio in a surface portion which is in contact with the plywood board, resulting in a rough state of the finished concrete outer surface. Since an erroneous decision may be made on defective hardening of the concrete in this case, prescribed painting is applied to the surface of the plywood board for reducing its water absorptivity. However, such a painted plywood board is high-priced and hence the cost is disadvantageously increased.
On the other hand, the metal form member can be hardly applied to general construction works since the executable range is limited due to a small degree of freedom in working, although the same has high strength. Further, the metal form member must be miniaturized due to its heavy weight, leading to inferior executability. Further, insufficient management leads to unusability due to rusting and/or deformation, and it is extremely difficult to repair such a rusted/deformed form member.
While the synthetic resin form member can provide an excellent concrete finished surface, further, the aforementioned form member described in Japanese Utility Model Laying-Open No. 62-54149, which comprises a plate member and solid prism-shaped projections similarly to the wood form member except that the same are made of synthetic resin, has a heavy weight and can be manufactured only by press molding due to limitation in its shape, with requirement for a high manufacturing cost.
Further, existent synthetic form members including those described in Japanese Patent Laying-Open Nos. 2-8459 and 5-59811 are not beyond the ranges of the shapes and functions of the wood and metal form members. Namely, the surfaces, the both side ribs and the back surfaces of such form members have only functions for serving as concrete molding surfaces, form member connecting members and reinforcement forming surfaces respectively, and hence only a single function is decided every surface in these existing form members. Thus, a synthetic resin form member can be used only in the same method as those for the remaining existent form members.
In addition, the conventional synthetic resin form member, which is manufactured by press molding, is insufficient in strength and high-priced, and hence the same is hardly put into practice under the present circumstances. Further, the conventional synthetic resin form member is inferior in workability for connection and demolition, since such members are connected with each other through nails or bolts and nuts.
In the conventional form member space holder described with reference to FIGS. 55 to 56C, on the other hand, the resin presser part 122a and the body part 122b of each attachment 122 are positioned on the concrete placing surface of each form member 70, and hence it is necessary to mount the separator 121 and the attachments 122 before fixing the positions of a pair of form members 70. Once the positions of the form members 70 are fixed, the separator 122 and the attachments 122 can be neither mounted nor demounted, leading to inferior workability.